First of all, think about what knowledge you are confused and interested in, so what kind of books have you borrowed? Then because the library is too big, you can't find it. Later, you asked the librarian about the books you borrowed. Then you found this book and borrowed it. The librarian tells you that this is a popular book that can be borrowed and gives you three days to borrow it. Then you must return it. Then you agreed and walked into the street.